1. Field of the Invention
The present invention relates to any lightweight reinforced extruded tubing for telescopic handles for trolley-type carry cases, wherein the first stage tube is reinforced by metal strips having apertures which are dimensioned and positioned to receive the spring biased locking pins of a multi-stage locking mechanism.
2. Description of the Related Art
Present day tube technology, particularly technology for the first (i.e., lowermost) stage of telescopic handles for carry cases has advanced in several stages. The following is a brief history of the developments of advancements in such tube technology.
First Generation
In general, the strength requirements of the pair of first stage tubular members which form the basis for a telescopic handle have always required a pair of tubes which are of sufficient strength to withstand the forces generally applied to them, not only during the upward and downward telescopic extension and collapsing action, but also while traveling with the carry case, particularly over rough terrain, stairways and the like. Additionally, when the first stage tubes are outside of the case, it is desirable that they match the case. For this reason, particularly for such applications, the outside of the tube was always made of a plastic material which matched the case.
In the past, the pair of tubular members which formed the first stage of the telescopic mechanisms for such applications were originally comprised of a pair of metal tubes, each tube being surrounded by a plastic extruded polyvinyl chloride (i.e., PVC) tube assembled to the metal tube so as to appear like plastic tubes to match the carry case. The inner metal tube provided the strength for the spring loaded pins that entered the apertures in the metal tube from the telescopic second and third stage handles. In particular, the metal tube was required in order to provide strength for reception of the pins into the apertures from the second and third stage tubes, since a plastic tube with such apertures would normally not have the strength to receive the pins or to support the forces applied thereto during use. Over time, such apertures, if provided in the plastic tube, would become elongated and worn. Furthermore, the metal tubes provided the strength required for traveling with the case; i.e., bending, tension, compression and shock loads. However, the metal tubes added unwanted additional cost and excessive weight to the entire case.
Second Generation
Subsequently an improved version of the first stage tubes was provided by simply individually molding a pair of plastic tubes of ABS (i.e., Acrylonitrile-Butadiene-Styrene) in individual molds. The individually molded tubes were stronger than the extruded tubes of the first generation. However they also needed to be reinforced by a metal tube inserted into the plastic tube as in the first generation. These metal tubes were also capable of carrying the loads from the spring loaded pins provided by the second and third stage telescoping tubes. As in the first generation tubes, the metal tubes also added strength and weight to the tube, and the carry case, as well.
One disadvantage however, of the molded tubes is that they needed to be custom molded for individually sized carry cases, thus increasing their production costs. For example, each pair of first stage tubes required an individualized molding process for each size carry case. This is in sharp contrast with the prior generation of extruded tubes which were simply cut to size for each style and size of carry case. Accordingly, it would appear that extruded tubes always provided a significant advantage over molded tubes. However, notwithstanding that fact, the present invention can be used with individually molded tubes as well.